1. Field of the Invention
The present invention relates to a vibration-isolating supporting structure which supports a second member at a first member via plural vibration-isolating apparatuses.
2. Description of the Related Art
Industrial vehicles (vehicles for construction, building, engineering, and vehicles for agriculture, and the like), which a worker (operator) rides in, have a cabin in which the worker rides. In assembling the cabin to the vehicle body, a vibration-isolating member is mounted between the cabin and the vehicle body due to the need to mitigate vibration, shock, noise and the like during traveling and during operation. Due to structural constraints on industrial vehicles in general, the cabin is generally set on a frame which structures a main body, and the vibration-isolating member is, of necessity, set at the upper side of the frame and the lower side of the cabin (refer to Japanese Patent Applications Laid-Open (JP-A) Nos. 5-125745 and 2001-323510).
Because the input of vibration, shock or the like propagates from the frame, the vibration, shock or the like is transferred to the cabin via the vibration-isolating member. However, the center of gravity position of the cabin is positioned higher than the supporting surface to which the vibration-isolating member is mounted. Therefore, there is the drawback that, the greater the distance from the vibration-isolating plane, the greater the “shaking” due to propagated vibration.
Because the “shaking” becoming great relates to a deterioration in the comfort of the ride, vibration-isolating members, which are filled with a viscous fluid and whose damping force is large, are often used as the vibration-isolating members in such applications. Note that making the springs hard can also make the “shaking” small, but works disadvantageously with respect to vibration transfer, and is also disadvantageous with respect to cutting-off noise which propagates into the cabin. Therefore, there is the trend toward demanding pliant supporting springs of a vibration-isolating member.
Further, there are also examples in which, in some vehicles, the vibration-isolating supporting plane is structured above the cabin roof and the cabin is supported in a state of being suspended (refer to JP-A No. 05-178586). However, the positional relationship with the center of gravity point of the cabin is the same as that described above, and there is the problem that the “shaking” cannot be kept small unless the damping force is made to be large, or the springs are made to be hard, or stoppers or the like are used.
In order to make the shaking of the cabin small, it has been thought to use a liquid-filled-type vibration-isolating apparatus having high damping force. However, the structure of this type of vibration-isolating apparatus is special, and is also expensive.
Further, from the standpoint of ensuring the safety of the worker in an industrial vehicle, cabin strength has been improved recently. The weight supported by the vibration-isolating member has increased, and, as the weight of the cabin has increased, the vibration energy on the springs also has become large, and there is the need for further improvement in the damping force.